<!DOCTYPE html>
<html>

<head>
    <meta charset="utf-8">
    <title>设置字体大小</title>
    <style>
        h1 {
            font-size: 250%;
        }

        h2 {
            font-size: 200%;
        }

        p {
            font-size: 100%;
        }
    </style>
</head>

<body>
    <h1>This is heading 1</h1>
    <h2>This is heading 2</h2>
    <p>This is a paragraph.</p>
</body>

</html>